NATURAL WAXES 321 



Although the present empirical forimila of C27H46O was proved, in 1888, 

 on the basis of an analysis of cholesterol acetate dibromide by Reinitzer,^"^^ 

 it was not until the period of the early thirties of this century that the 

 structural formulas of cholesterol and other sterols were first established. 



In addition to cholesterol, other sterols have also been known for a long 

 time. For example, in 1811 Braconnot^^* isolated a product from mush- 

 rooms which he named adipocire. Vauquelin^^^ referred to this same prod- 

 uct as fimgine, while Gobley^-^ gave it the name agaricine. It remained 

 for Tanret^^^'^^^ to coin the term ergosterine for it, and to point out its 

 relationship to cholesterol. 



(h) Classification of Sterols. Thanks to the development of our knowl- 

 edge on the structural relationships of the various sterols, and in view of 

 the increased information now available on their distribution in nature, a 

 satisfactory classification based upon the latter data has recently been 

 drawn up. This classification is as follows : 



1. Zoosterols or animal sterols. This group includes cholesterol, coprosterol, allo- 

 cholesterol, and dihydrocholesterol. 



2. Phylosterols or plant sterols characteristic of the higher plants or phanerogams. The 

 common sterols included in this category are sitosterol, stigmasterol, and brassicasterol. 



3. Mycosterols or sterols from lower plants (especially fungi). The general plant group 

 in which the mycosterols occm* includes the cryptogams. The best known example in 

 this group is ergosterol. Other representatives are zymosterol, dihydroergosterol, and 

 fucosterol. 



(c) Structure and General Properties of the Sterols. Although the correct 

 empirical formula for cholesterol was established many years ago by 

 Reinitzer,!-^ the first approximation to the structural formula was not pro- 

 posed until 1928. This Wieland formula^^^ was soon shown to require 

 modification. This investigator realized that the position to which the 

 ethyl group was attached was not unequivocally proven, and the task of 

 placing the two "homeless" carbon atoms continued to be the objective of 

 Wieland and collaborators, according to Rosenheim and King.^"^ As a 

 result of the new conception of the stiticture of the hydrocarbon, cholane, 

 proposed by Rosenheim and King,^^"""^ a new formula for cholesterol was 

 proposed by these same workers ^^°~^^^ and by Wieland and Dane.^^^ This 

 formula has now been unanimously accepted. The revised stmcture was 



123 F. Reinitzer, Monatsh., 9, 421-441 (1888). 



124 H. Braconnot, Ann. chim. phys. [1], 79, 265-304 (ISU). 



125 U. Vauquelin, Ann. chim. phijs. [1], 80, 5-25 (1813). 



126 M. Goblev, ./. pharm. chim. [3], 29, 81-91 (1856). 

 12' C. Tanret, Compl. rend., 108, 98-100 (1889). 



128 C. Tanret, Ann. chim. phys. [6], 20, 289-297 (1890). 



129 H. Wieland, Z. angew. Chem., 42, 421-424 (1929). 



1^ O. Rosenheim and H. King, Chemistry & Industry, .51, 464-466 (1932). 

 1" O. Rosenheim and H. King, Nature, 130, 315 (1932). 



132 O. Rosenheim and H. King, J. Soc. Chem. Ind., 52, 299-301 (1933). 



133 H. Wieland and E. Dane, Z. physiol. Chem., 210, 268-281 (1932). 



